1. Technical Field
The present disclosure relates to a reference frequency calibration module, in particular to a reference frequency calibration module with crystal-less and apparatus using the same.
2. Description of Related Art
Currently, the universal serial bus (USB) is a general transmission interface in the computer system or portable electronic device. The connection mode of the USB is amiable to user and the speed of the USB is fast, thus the USB has gradually become the standard of the transmission interface. The connection interface of each electronic apparatus mainly applies the USB to connect with the computer system, such as portable communication device, reader, keyboard, or mouse, etc.
In practice, a reference frequency is required to be a clock reference criterion of the operating system in the communication system. Generally, the transmission frequency of the USB needs to satisfy the requirement such as low jitter, high frequency accuracy, unchanged with supply voltage and the temperature variation. Therefore, the traditional electronic apparatus usually generates the stable frequency (about 50 ppm frequency error) by cooperates with the active oscillator or the passive crystal, so as to cause the cost and circuit area of the electronic apparatus raising.